According to scientists, choosing a plant-based diet is the biggest way to reduce our environmental impact. Vegan diets require less land, water, and resources compared to traditional animal agriculture—and they also help reduce greenhouse gas emissions and deforestation associated with livestock farming.

Of course, in the animal kingdom, veganism is nothing new. But the dietary habits of herbivores extend far beyond mere sustenance. Here are four ways that plant-eating animals help to foster a more resilient planet.

1. Herbivores as firefighters

Herbivores function as natural fire suppressants, playing a crucial role in mitigating the risk of wildfires through their inherent behaviours of consuming and trampling vegetation. In 2021, global wildfires released a record high of 1.76 billion tons of carbon dioxide into the atmosphere. That figure would have been much higher without the help of herbivores. Their foraging activities prevent the accumulation of dry and flammable plant material. Grazing animals such as deer, bison, wildebeest, rhinos and elephants, (the last of which are known to knock down whole trees to get to the nutritious leaves and roots) therefore act as custodians of their habitats, reducing the fuel load for potential fires.

By selectively feeding on grasses, shrubs, and other vegetation, herbivores not only limit the abundance of combustible materials but also alter the landscape structure itself. Their constant movement and trampling creates open spaces, which prevents the rampant spread of fires. These natural firebreaks act as a first line of defence against the rapid advancement of flames.

Moreover, herbivores promote healthier vegetation that is less susceptible to ignition in the first place, through a process called nutrient cycling, which neatly brings us to the next order of business

2. Herbivores as Climate Stabilisers

Herbivores play a vital role in nutrient cycling and carbon sequestration through their digestive processes. When large herbivores graze on vegetation they convert the way carbon is stored. They quickly digest their plant-based meal and produce nutrient-rich dung. Not only does this increase soil fertility and help more carbon-absorbing plants to grow, but when the dung decays, the carbon that was previously stored in the plants becomes locked away in the soil instead.

The significance of this lies in the fact that soil serves as a more stable and long-term carbon sink. Unlike plants and animals, which quickly release carbon into the atmosphere through processes of decomposition, burning, or simply by breathing, soil provides a more protective environment for carbon. A whopping 2,500 billion metric tons of it is stored in soil, compared to560 billion tons of carbon in all plant and animal life.

New studies indicate that the grazing activities of wild herbivores might also trigger the release of substances from plant roots, which contribute to the stabilization of soil carbon. This phenomenon is notably evident in the Serengeti region of East Africa. Researchers observed that the resurgence of wildebeest populations following a virus epidemic in the 1960s had significant environmental implications. The additional storage of carbon beneath the soil, as a result of the wildebeests’ grazing, enabled the expansive grasslands to sequester more carbon than they released. Enough, in fact, to nearly offset the annual carbon emissions from fossil fuel use in East Africa.

This highlights the intricate connections between herbivores and carbon sequestration. By locking away carbon in the soil, herbivorous animals help mitigate climate change.

3. Herbivores as Nature’s Gardeners

Herbivores play a huge role in increasing ecosystem productivity. Like weeding a garden, the grazing and browsing activities of herbivores prevents overgrowth and makes way for new plants to grow. Moreover, their dung acts as a natural fertiliser, supporting the growth of a wide range of plants and contributing to the overall health of ecosystems.

For all their innovations, one thing plants can’t do is relocate themselves from one place to another. So they use animals instead, tempting them with nutrient-rich fruits, or producing seeds with hooks/burs that catch on the fur of passing mammals. In the tropics, up to 90% of tree species rely on animals for seed dispersal and in temperate zones it’s about 50%. The animals disperse seeds away from the parent plant, sometimes considerable distances. Elephants, for example, can travel up to 100 kilometres or 60 miles carrying several different types of seed in their gut. The seeds are then excreted in their dung, which provides a ready-made package of essential nutrients within which seedlings can sprout [below left]. Birds may also browse for seeds in herbivore dung [below right], and their flights help disperse the seeds across even greater distances.

[Below] A southern cassowary feeds on fruits. The seed are then present in the cassowary’s dung and later germinate.

The natural gardening that herbivores provide is so important that some plant species completely rely on them for their survival. Arguably one of the most important seed dispersers is the tapir. Not only can it disperse a huge diversity of seeds across long distances, but it may also be the last lifeline for many plant species, which previously dispersed their seeds in the guts of extinct animals.

Weeding, fertisling and seed dispersal are not the only gardening habits herbivores carry out. Many plant-eating animals, including bats, birds and insects, fulfill a crucial role of pollinating flowering plants, facilitating the reproduction and regeneration of vegetation.

4. Herbivores as Thermostats

Amazingly, herbivores contribute to the Earth’s cooling mechanisms by influencing the reflectivity of the planet’s surface. Grazing, particularly in open grasslands, exposes more reflective surfaces, such as bare soil and short grass, which have higher ‘albedo’ – the ability to reflect sunlight. High-albedo surfaces bounce more solar radiation back into space, reducing the absorption of heat by the Earth.

This effect is especially evident in the Arctic, where grazing exposes very bright and reflective snow-covered ground. Large animals here also compact snow with their hooves, reducing its insulating effect and keeping soil below freezing point. This protects permafrost and prevents carbon rich material in soil from melting and releasing carbon dioxide. The impact of grazers is so significant that it is estimated that the extinction of mammoths and other large Arctic herbivores increased the temperature of Siberia and Beringia by up to 1°C.

Even the reflectivity of the atmosphere is affected by large herbivores. Browsing and grazing affects tree cover and therefore evapotranspiration (the process of water evaporation from plants into the atmosphere). When vegetation cover is diminished, and soil moisture is scarce, the likelihood of soil erosion and the release of dust into the atmosphere increases. Dust particles scatter solar radiation and promote the formation of clouds, which act as a natural sunscreen by absorbing and reflecting sunlight back into space.

Herbivores, therefore, reduce the amount of solar radiation that reaches the Earth’s surface. Their influence on planetary temperatures further demonstrates their important role in the fight against climate change.

Can Herbivores Save the World?

While it might be an exaggeration to claim that herbivorous animals can single-handedly “save the world,” their positive impact on the planet is undeniable. In essence, herbivores act as stewards of the natural world, shaping landscapes and fostering biodiversity. They are ecological regulators, firefighters and seed disperses. They contribute to nutrient cycling, soil fertility, and carbon sequestration. Their dietary habits even protect us from climate change and help cool the earth.

A world without herbivores would be a disaster for any natural ecosystem. But, according to one 2020 study, about one in four species of herbivores (25.5 percent) are considered threatened, endangered or vulnerable to extinction. In the absence of those herbivores, the beneficial impacts they provide would diminish. And if that wasn’t bad enough by itself, it could also negatively impacts the adaptability of plant species. In 2022, researchers showed that plants dispersed by animals now face, on average, a 60% reduction in their seed-spreading capabilities compared to the pre-human era. In some cases, the plants’ capacity to migrate to suitable habitats is reduced by as much as 95%–rendering them less equipped to adapt to climate change. The cause? Diminishing populations, relocation, or extinction of animals responsible for seed dispersal. The disappearance of large mammals and birds is especially problematic, since they transport seeds over considerable distances. With fewer animals available to move these seeds, plants are more vulnerable to climate change than ever.

 

[Above] It is estimated that most African savanna elephant populations are currently at less than a quarter of ecosystem capacity. The biggest threat to them is human-wildlife conflict. In this image, a breeding herd navigates burning floodplains. Fires are started by people in the dry season to burn the grass and make it easier to cast fishing nets when the floods arrive. These fires can cut off access routes to water and push elephants into areas where they are at danger from hunting and poaching.

 

Globally, an even bigger threat to wildlife than climate change, is habitat loss. And the biggest driver of habitat loss is agriculture. The vast majority of global farmland—more than 80%—is currently used for livestock which produces just 18% of food calories consumed. As Sir David Attenborough put it in the ‘Humans’ episode of ‘Plant Earth III’, if everyone in the world was vegan “we could still produce enough to feed us—but do so using a quarter of the land. This could free up an area the size of the United States, China, the European Union and Australia, combined – space that could then be given back to nature.”

In other words, perhaps it’s time we took more inspiration from the herbivores of the world.

 

[Above] The substitution of large native herbivores such as elephants, rhinos, and zebras with domestic livestock (particularly cattle) might have resulted in a more than twofold increase in methane emissions across sub-Saharan Africa. Methane has considerably greater greenhouse gas potency than CO2 in the short term; within the initial 20 years of emission, it traps roughly 80 times more heat than CO2. This fact alone highlights the need to restore large wild herbivore populations to their ecosystems.